Posted
by
kdawson
on Wednesday August 04, 2010 @04:06AM
from the sweating-it-out dept.

GWMAW writes "NASA Astronauts will conduct a spacewalk on Thursday to repair part of the cooling system of the International Space Station. The cooling system is essential for maintaining the temperature inside the station. There are two 'loops' in the system, one that uses water and draws heat from the inside of the station, and one uses ammonia and dumps the heat into space. Ammonia is used because it freezes at a much lower temperature than water. On Saturday the pump that controls the flow of ammonia through the system shut down."

Typical Slashdot, a bit behind. This is the press release they sent out on Tuesday.

Aug. 03, 2010

Stephanie SchierholzHeadquarters, Washington

James HartsfieldJohnson Space Center, Houston

MEDIA ADVISORY: M10-107

NASA MOVES SPACE STATION REPAIR SPACEWALK TO FRIDAY, SETS BRIEFINGS

HOUSTON -- The first of two spacewalks by NASA astronauts to replace afailed ammonia pump on the International Space Station has beendelayed by 24 hours to Friday, Aug. 6. A second spacewalk is plannedfor Monday, Aug. 9, to complete the repairs.

Flight controllers and station managers made the decision Monday nightafter reviewing proposed timelines, final procedures for the repairwork, and the results from a spacewalk dress rehearsal conducted inthe Neutral Buoyancy Laboratory near NASA's Johnson Space Center inHouston.

NASA Television coverage of both spacewalks will begin at 5 a.m. CDT.Wheelock and Caldwell Dyson are expected to begin the spacewalks fromthe Quest airlock at 5:55 a.m. Friday's spacewalk will be the fourthfor Wheelock and Caldwell Dyson's first.

Approximately two hours after the conclusion of each spacewalk, NASATV will broadcast a briefing from Johnson. The briefing participantswill be Mike Suffredini, International Space Station program manager;Courtenay McMillan, Expedition 24 spacewalk flight director; andDavid Beaver, Expedition 24 spacewalk officer.

Reporters may ask questions from participating NASA locations, andshould contact their preferred NASA center to confirm participation.Johnson will operate a telephone bridge for reporters with validmedia credentials issued by a NASA center. Journalists planning touse the service must contact the Johnson newsroom at 281-483-5111 nolater than 15 minutes prior to the start of a briefing. Phone bridgecapacity is limited and will be available on a first-come,first-serve basis.

Engineers and flight controllers continue to review data on thefailure, which resulted in the loss of one of two cooling loopsaboard the station. This caused a significant power down and requiredadjustments to provide the maximum redundancy possible for stationsystems. The systems are stable, and the six crew members aboard arenot in any danger.

Wheelock and Caldwell Dyson originally were scheduled to perform aspacewalk to outfit the Russian Zarya module for future robotics workand prepare the station for the installation of a new U.S. permanentmultipurpose module. However, because of the importance of restoringredundancy to the station's cooling and power systems, the two newspacewalks will be dedicated to the pump module replacement.

Without thermal controls, the temperature of the orbiting Space Station's Sun-facing side would soar to 250 degrees F (121 C), while thermometers on the dark side would plunge to minus 250 degrees F (-157 C). There might be a comfortable spot somewhere in the middle of the Station, but searching for it wouldn't be much fun!

Maybe you cannot lose hear through convection but, in space, you can certainly loose heat by radiation. Deep space background is around 3K and a deep space radiative cooler is a very good and efficient way to cool something in space.

You cannot do any thermal analysis of an object in space without taking the radiative part into account.

An uninsulated space suit in a vacuum wouldn't feel very cold on the inside as long as the suit doesn't touch anything on the outside.

What were the physics involved in the Apollo 13 mission when they were getting very cold after turning off the heaters in the spacecraft, using the LEM as a lifeboat?

When it comes to using power, it is easier to heat something than to cool it. The apollo spacecraft was designed to be passively cool in the sense that it reflected enough of the sunlight striking it to need as small amount of heating from batteries to stay warm. If it had absorbed more heat from the sun it would have required active cooling which is very expensive in energy terms.